I must suck really bad cuz it took me forever to playtest the first 3 chapters before I started working on mine cuz the 'minigames' are H.A.R.D. lol
I know the first one in Christophomicus' chapter seemed pretty difficult to me. The last parts of Ohlichris' chapter were pretty hard too (what's up with all thse chris' and their hard minigames
). I'm not saying they were too hard though.
Remember that easy minigames are just as cool as hard ones! As long as they're fun to play, I'd rather have too easy than too hard minigames. If you think one your minigame is turning out to be a bit too hard for the average player, give him an alternative route or an option to skip the minigame. Or maybe have him choose between two minigames, a hard one or an easy one. You could also have the player choose the difficulty for the minigame.